Steel strip, as it leaves a hot rolling mill, is covered with iron oxide mill scale. These iron oxides are removed by passing the steel strip through a mechanical descaler followed by immersion in a pickle tank where it is contacted by hot hydrochloric or sulfuric acid which removes the oxides.
Steel strip as it leaves the pickle tank will be at a temperature of about 160.degree. to 180.degree. F. and the surface of the steel will be extremely reactive so that it must be coated immediately with a pickle oil to prevent reoxidation.
The pickle oils used in the steel mills today are light hydrocarbon oils containing a substantial quantity of grease. These light pickle oils have three disadvantages. First, they drip from the coiled steel strip creating a fire and accident hazard on the floor of the steel mill. Secondly, as the pickle oil is depleted from the steel strip, its ability to protect against atmospheric corrosion is greatly reduced. Third, since the pickle oil provides the lubricant in the first stand of a cold rolling mill, the loss of the lubricating oil by dripping will have to be replaced by another lubricant. Similar disadvantages are observed in the slushing oils in use today.